KR100289027B1 - Method and apparatus for controlling electromagnetic valve in industrial vehicle - Google Patents

Abstract

Method and apparatus for preventing solenoid 18 from being heated by an exciting current. When the hydraulic cylinder 12 is extended and retracted, the controller 26 controls the high-side driver 32 to transfer the moving current to the solenoid 18 so that the solenoid valve 16 is moved to the connecting position. Thus, the controller 26 controls the high-side driver to transmit the holding current to the solenoid 18 so that the valve body 160 is held at the connecting position. The moving current and the holding current are pulse waves. The duty ratio of the holding current is less than the duty ratio of the moving current.

Description

Method and apparatus for controlling electromagnetic valve in industrial vehicle

The present invention relates to a mechanism for controlling the pivoting of a rear wheel shaft of an industrial vehicle, such as a forklift, and more particularly to a method and apparatus for controlling a solenoid valve in a hydraulic circuit of a pivot control mechanism.

In a typical industrial vehicle such as a forklift, the axle for supporting the rear wheels pivots against the body frame to stabilize the body frame. However, if the vehicle is steered to change direction, the pivoting of the rear axle may cause the body frame to tilt and thus the vehicle becomes unstable. Therefore, the vehicle has a mechanism for locking the rear wheel axle when the vehicle changes direction.

The axle locking mechanism includes a hydraulic circuit having a hydraulic cylinder. The hydraulic cylinder is disposed between the body frame and the rear wheel shaft and has two oil chambers. The oil chambers are interconnected by oil passages. The solenoid valve is disposed in the oil passage. Pivoting of the rear axle stretches and retracts the hydraulic cylinder. In order to control the pivoting of the rear axle, the expansion and contraction of the hydraulic cylinder is controlled. When the rear axle is pivoted, the solenoid valve opens to allow the oil chambers to communicate with each other to allow the hydraulic cylinder to reciprocate. On the other hand, when the rear wheel shaft is locked, the solenoid valve blocks the oil chambers from being interconnected.

The solenoid valve is a two-way switch valve having a valve body moved between a connecting position allowing the oil chambers to communicate with each other and a blocking position for blocking the oil chamber. The position of the valve body is determined by the equilibrium between the spring force used to pull the valve body toward the shutoff position and the spring force of the solenoid pulling the valve body toward the connecting position. When the solenoid is not excited, the spring force places the valve body in the shut off position. When the solenoid is excited, the force of the solenoid suppresses the spring force and puts the valve body in the connecting position. The solenoid valve is controlled by a controller which controls the pivoting of the rear wheel shaft.

When the forklift carries a relatively heavy loading load in a relatively high position, the controller does not excite the solenoid. Thus, the valve body is in the shut off position and the rear wheel shaft is locked. When the forklift carries a relatively light loading load at a relatively low position, the controller excites the solenoid. This puts the valve body in the connecting position and allows the rear axle to pivot.

As described above, if the solenoid is not excited, the solenoid does not put the valve body in the connecting position. Therefore, when the solenoid fails, the rear wheel shaft can be prevented from pivoting.

The solenoid valve is exposed to heat from the vehicle engine. Oil in the hydraulic circuit flows when the rear axle is pivoted. Frequent pivoting of the rear axle raises the temperature of the oil, which also raises the temperature of the circuit. Continuously pivoting the rear axle shaft over the entire extended period, ie, when the solenoid is excited for a long time, the temperature of the solenoid rises. Therefore, the solenoid valve overheats, causing a solenoid failure.

It is an object of the present invention to provide a method and apparatus for controlling a solenoid valve actuated by a solenoid by preventing the solenoid from overheating.

To realize this object, the present invention includes a power source, a solenoid excited by the power source, and a valve body switched between a first position and a second position. The valve body is pulled toward the second position. The method comprises the steps of a) supplying a moving current to the solenoid to move the valve body from the second position to the first position, and b) holding a holding current of a value less than the moving current to hold the valve body in the first position. after step a) feeding the solenoid.

The present invention also provides a controller for controlling the solenoid valve. The controller includes a driver and a processor. The driver applies a voltage to the solenoid. The processor sends a command to the driver indicating the value of the voltage to apply to the solenoid. When moving the valve body from the second position to the first position, the processor sends a movement command signal to the driver to apply the movement voltage to the solenoid for a predetermined period. When the valve body is held in the first position, the processor calculates a holding current that is somewhat larger than the minimum current for holding the valve body in the first position, and sends a holding command signal to the driver for applying the holding voltage in a later period. do. The holding voltage generates a holding current in the solenoid.

Other aspects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings which illustrate embodiments of the principles of the invention.

1 is a circuit schematic diagram of a controller for controlling a solenoid valve according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating a pivot control mechanism having the valve controller of FIG. 1. FIG.

3 is a schematic view showing a hydraulic circuit of the pivot control mechanism of FIG.

4 is a timing chart showing a pattern of the voltage pulse output from the controller of FIG.

Fig. 5 is a timing chart showing a pattern of voltage pulse output from the valve controller according to the second embodiment.

6 is a circuit schematic diagram of a controller for controlling a solenoid valve according to a third embodiment of the present invention;

A first embodiment of a controller 26 for controlling the solenoid valve will be described with reference to FIGS. The valve controller 26 shown in FIGS. 1 to 4 is used in a pivot control mechanism for controlling the rear wheel shaft 11 of the forklift. However, the controller 26 can be used in particular for other pivot control mechanisms to be exposed to overheating.

As shown in FIG. 3, the body frame 10 of the forklift is pivotally supported on the rear wheel shaft 11. The rear wheel 9 is connected to the rear wheel shaft 11. The hydraulic cylinder 12 is disposed between the vehicle body frame 10 and the rear wheel shaft 11. The cylinder 12 includes a housing 13 and a piston rod 14. The housing 13 is coupled to the vehicle body frame 10 and the piston rod 14 is connected to the rear wheel shaft 11. The piston rod 14 includes a piston head (not shown) embedded in the housing 13. The piston head slides in the longitudinal direction of the housing 13.

The interior of the cylinder 12 is divided into a first oil chamber R1 and a second oil chamber R2 by a piston head. The first oil chamber R1 is disposed closer to the vehicle body frame 10 and the second oil chamber R2 is disposed closer to the rear wheel shaft 11. The first and second oil chambers R1 and R2 are connected to each other in fluid by the oil passage 15. The oil passage 15 includes a solenoid valve 16 which interconnects and shuts off the oil chambers R1 and R2. That is, valve 16 allows or prevents fluid communication between chambers R1 and R2.

The solenoid valve 16 is a two-way switch valve and preferably has a valve body 160. The valve body 160 is switched between the cutoff position 16e and the connection position 16f. The valve 16 has four ports 16a, 16b, 16c, 16d. The port 16a is connected to the oil chamber R2 by the oil passage 15. The port 16b is connected to the oil chamber R1 by the oil passage 15. Ports 16c and 16d are connected to accumulator 19 which stores hydraulic oil.

When the valve body 160 is in the shutoff position 16e, the ports 16a and 16b are blocked as shown in FIG. In this state, the hydraulic oil is prevented from flowing between the chambers R1 and R2. Thus, the piston rod 14 is locked relative to the housing 13 and the rear wheel shaft 11 cannot be pivoted. When the valve body 160 is in the connecting position 16f, the ports 16a and 16b are interconnected by the ports 16c and 16d and the accumulator 19. This allows hydraulic oil to flow between the chambers R1 and R2. Thus, the piston rod 14 is movable with respect to the housing 13 and the rear wheel shaft 11 is pivotable with respect to the body frame 10.

The solenoid valve 16 includes a coil spring 17 and a solenoid 18. The coil spring 17 pulls the valve body 160 toward the cutoff position 16e. When excited, the solenoid 18 moves the valve body 160 against the spring 17 force and moves the valve body 160 to the connecting position 16f.

The current required to move the valve body 160 from the cutoff position 16e to the connecting position 16f or the first excitation current PD1 is the current required to hold the valve body 160 at the connecting position 16f. Or greater than the second excitation current PD2.

As shown in FIG. 2, the controller 26 is attached to the vehicle body frame 10. The controller 26 is connected to the battery 27 to control the valve 16. The battery 27 supplies the power supply voltage VB to the solenoid 18 and the controller 26.

As shown in FIG. 2, the fork 21 is fixed to the inner mast 22. The inner mast 22 is supported by the mast 20. The mast 20 includes a fork position sensor 23. The fork position sensor 23 is preferably a limit switch for detecting the vertical position of the fork 21. The fork 21 is raised and lowered by two lift cylinders 24. One of the lift cylinders 24 has a pressure sensor 25. The pressure sensor 25 detects the pressure of oil in the associated lift cylinder 24. The detected pressure corresponds to the load on the fork 21. The solenoid 18, the fork position sensor 23 and the pressure sensor 25 are electrically connected to the controller 26.

The electrical circuit of the valve controller 26 will now be described.

As shown in FIG. 2, the fork position sensor 23 is connected to a controller 26. The fork position sensor 23 is turned off when the fork 21 is raised above the predetermined height HO or turned on when the fork 21 is positioned at a position lower than the predetermined height HO. The fork position sensor 23 transmits the height signal SH to the controller 26. The value of the height signal SH represents the vertical position of the fork 21 with respect to the height H0. The pressure sensor 25 detects the load W of the loading load on the fork 21. The pressure sensor 25 sends an analog signal SW to the controller 26. The analog signal SW corresponds to the load W. The controller 26 applies the excitation voltage VP based on the height signal SH, the load signal SW and the power supply voltage VB to the solenoid 18. The applied excitation voltage VP generates an excitation current PD on the solenoid 18.

As shown in FIG. 1, the controller 26 includes a voltage detector 30, a microcomputer 31, and an intelligent high-side driver 32. The voltage detector 30 includes resistors 33 and 34. The voltage detector 30 detects the voltage VB of the battery 27 and transmits a signal Vb indicating the detected voltage VB to the microcomputer 31.

The microcomputer 31 includes a central processing unit (CPU) 31a, analog-to-digital (A / D) converters 35 and 36, input interfaces 37 and 38 and pulse width modulation ( PWM) circuit 39. The voltage signal Vb is input to the CPU 31a through the A / D converter 35. The height signal SH is input to the CPU 31a via the input interface 37. The load signal SW is input to the CPU 31a through the A / D converter 36.

The CPU 31a generates the load signal SW, for example, the height signal SH at a predetermined time interval based on the frequency of 3 kHz and the command signal SD based on the voltage signal Vb. The PWM circuit 39 generates a pulse width modulation PWM signal PS based on the command signal SD and transmits the PWM signal PS to the high-side driver 32. The PWM signal PS is a pulse signal that varies between high voltage and low voltage. The duty ratio of the pulse signal PS is D%.

The high-side driver 32 prevents solenoid 18 from receiving an overvoltage from battery 27. The high-side driver 32 is preferably a conventional semiconductor chip (eg, VN06 manufactured by SGS Thomson). The high-side driver 32 has an input terminal IN, a power supply terminal VCC, an output terminal OUT, and a diagnostic terminal DIAG (hereinafter referred to as a diag terminal). The power supply terminal VCC finally receives a power supply voltage VB (for example 12 volts) applied to the solenoid 18. The input terminal IN receives the PWM signal PS. Output terminal OUT is connected to solenoid 18 and flywheel diode 40.

High-side driver 32, solenoid 18 and flywheel diode 40 are preferably co-grounded. The high-side driver 32 modulates the voltage VB to the excitation voltage VP and the pulse-width modulation of the direct voltage VB based on the PWM signal PS in order to make the duty ratio D%. Perform. The excitation voltage VP is output from the output terminal OUT and supplied to the solenoid 18 as the excitation current PD.

In this modulation, the supply voltage VB is not actually reduced to obtain the excitation voltage VP. To be honest, the voltage of each pulse of the excitation voltage VP is equal to the power supply voltage VB. However, each pulse of the excitation voltage VP is very short (several milliseconds). Therefore, the apparent value of the excitation voltage VP is equal to the voltage VB multiplied by the duty ratio D. For example, when the duty ratio D of the PWM signal PS is 0%, the value of the excitation voltage VP is 0 V (= VE x 0). When the duty ratio D is 100%, the excitation voltage Vp is equal to the power supply voltage VB. If the duty ratio is 60%, the excitation voltage VP is equal to the power supply voltage VB. However, the apparent value of the excitation voltage VP is equal to 0.6 VB, which is multiplied by 60% of the voltage VB.

The high-side driver 32 has a self diagnostic function. The diag signal VD is output from the diag terminal DIAG every time a pulse signal is input to the input terminal IN. That is, the diamond signal VD is a pulse signal having the same duty ratio as the PWM signal PS.

When the voltage at the input terminal (IN) is low and the voltage at the output terminal (OUT) is 0 volts, or when the voltage at the input terminal (IN) is high, the voltage at the output terminal (OUT) is the supply voltage (VB), and the high-side driver. When there is no failure in 32, the high-side driver 32 outputs a diag signal VD having a high voltage through the diag terminal DIAG. That is, the diamond signal VD having a high voltage indicates that the high-side driver 32 has no fault.

When the level of the signal at the input terminal IN does not correspond to the level of the signal output from the output terminal OUT, that is, when the voltage at the input terminal IN is low and the voltage at the output terminal OUT is the power supply voltage. Alternatively, when the voltage at the input terminal IN is high and the voltage at the output terminal OUT is 0 volts, the solenoid 18 is electrically open due to the interruption of the coil or otherwise shorted. For example, when the solenoid 18 is shorted, the output terminal OUT outputs the power supply voltage VB constantly. This overheats solenoid 18 and as a result causes the solenoid 18 to shut off. In this state, the high-side driver 32 outputs a diamond signal VD having a low voltage, which indicates that there is a failure.

The flywheel diode 40 prevents the controller 26 from being blocked by back electromotive force based on the inductance of the solenoid 18.

When the ignition switch (not shown) is turned on, the microcomputer 31 starts to operate. The microcomputer 31 executes a predetermined control program at predetermined intervals. The control program includes a routine for controlling the pivoting of the rear wheel 11.

The microcomputer 31 determines whether the load W of the loading load is greater than or equal to the reference value W0 and whether the fork position H is greater than the reference value H0 based on the height signal SH and the load signal SW. Determine if it is the same. If the load W is greater than or equal to the reference value W0 and the vertical position H is greater than or equal to the reference value H0, the microcomputer 31 has a relatively high position of the fork 21 and rests on the fork 21. It is determined that the load is relatively heavy. In this case, the controller 26 suppresses the flow of current to the solenoid 18 and thus prevents pivoting of the rear wheel shaft 11. While the controller 26 does not supply current to the solenoid 18, the microcomputer 31 does not output the command signal PS. In this case, the voltage applied to the input terminal IN is low, and the high-side driver 32 continues to output the diag signal VD having a duty ratio of 100% from the diag terminal DIAG. The microcomputer 31 determines whether the solenoid 18 has a fault based on the diag signal VD. If the solenoid 18 is shorted, for example, the microcomputer uses an alarm device (not shown) to inform the driver of the failure of the pivot control mechanism.

On the other hand, if the load W is smaller than the reference value W0 or if the fork position H is smaller than the reference value H0, the microcomputer 31 has a relatively high position of the fork 21 and the fork 21 Judging that the load is not relatively heavy on the stomach. In this case, the controller 26 allows the hydraulic cylinder 12 to expand or contract and thus allow the pivot of the rear wheel shaft 11.

At this time, the controller 26 applies the excitation voltage VP to the solenoid 18, as shown in FIG. The excitation voltage VP has two values VP1 and VP2. The first excitation voltage VP1 is applied for a predetermined period T1 (eg, 1 second). Thereafter, the second excitation voltage VP2 is applied to the solenoid 18. The first voltage VP1 generates the first excitation current PD1 in the solenoid 18. The first excitation current PD1 moves the valve body 160 to the connecting position 16f. The second voltage VP2 generates the second excitation current PD2 in the solenoid 18. The second current PD2 keeps the valve body 160 at the connection position 16f. As described above, the low voltage value is required to hold the valve body 160 at the connecting position 16f than is required to move the valve body to the connecting position 16f.

When the CPU 31a outputs the first command signal SD1 having a duty ratio of 100% to the PWM circuit 39 during the T1 period, the controller 26 supplies the first current PD1 to the solenoid 18. do. That is, while receiving the signal SD1, the PWM circuit 39 supplies the PWM signal PS1 having a duty ratio of 100% during the time T1. The high-side driver 32 then applies the power supply voltage VB to the solenoid 18 as the excitation voltage VP1 for a time T1. Therefore, the first exciting current PD1 is supplied to the solenoid 18 for the time T1.

The first excitation current PD1 is preferably equal to the rated operating current of the solenoid valve 16. The time T1 at which the current PD1 is supplied to the solenoid 18 is a time long enough to move the valve body 160 from the cutoff position 16e to the connection position 16f.

On the other hand, in order to supply the second excitation current PD2, the CPU 31a outputs the second command signal SD2 to the PWM circuit 39. The second command signal SD2 indicates that the duty ratio Dh% is (Dh <100). The PWM circuit 39 outputs the second PWM signal PS2 to the high-side driver 32 based on the second command signal SD2. The high-side driver 32 modulates the direct voltage VB to the second excitation voltage VP2 based on the duty ratio Dh, and applies the second excitation voltage VP2 to the solenoid 18. The voltage VP2 generates the second excitation current PD2 in the solenoid 18. The second exciting current PD2 generates a force that acts on the force of the coil spring 17. In particular, the value of the current PD2 is large enough to hold the valve body 160 in the connecting position 16f against the force of the coil spring 17. The second excitation current PD2 has a smaller value than the first excitation current PD1.

In a preferred embodiment of the present invention, the duty ratio Dh is calculated by the CPU 31a using the following equation (1).

Dh (%)> Ih / (VB / Rsol) x 100

In Equation 1, Ih is a minimum current for maintaining the valve body 160 at the connecting position 16f. Rsol is the internal resistance of solenoid 18 at the maximum possible temperature Tmax of solenoid valve 16. That is, when calculating the duty ratio Dh, the internal resistance of the solenoid 18 is used at the maximum temperature Tmax of the valve 16.

The value of VB / Rsol represents the value of the current when the voltage VB is applied to the resistor Rsol. Typically, the resistance of the material increases with increasing temperature. That is, the value Rsol is greater than the resistance of the solenoid 18 under normal temperature conditions. Therefore, the duty ratio Dh is set such that the second excitation current is larger than the minimum current Ih and smaller than the current when the voltage VB is applied to the solenoid 18. That is, the CPU 31 sets the duty ratio so that (Ih &lt; PD2 &lt; PD1) is satisfied. In addition, since the CPU 31a checks the value of the power supply voltage VB, the second excitation current PD2 is always set larger than the minimum current Ih. Preferably, the second excitation current PD2 is slightly larger than the minimum current Ih.

The operation of the valve controller will now be explained.

When the ignition switch is turned on, the microcomputer 31 executes the pivot control program at predetermined intervals. If the fork height H is greater than or equal to the reference value H0 and the load W is greater than or equal to the reference value W0, the microcomputer 31 sends the PWM signal PS to the high-side driver 32. Do not print. In this state, the high-side driver 32 does not output the excitation current PD to the solenoid 18. Thus, the valve body 160 is held in the shutoff position 16e, which suppresses the movement of the cylinder 12. Thus, the rear wheel shaft 11 is locked against pivoting.

When the fork height H is lower than the reference value H0 or the load W is lower than the reference value W0, the microcomputer 31 sends the PWM signal PS from the PWM circuit 39 to the high-side driver ( 32). Then, as described above, the high-side driver 32 applies the first excitation voltage VP1 and the second excitation voltage VP2 from the output terminal OUT to the solenoid 18. This generates the first and second excitation currents PD1 and PD2.

When receiving the first excitation current PD1, the solenoid 18 moves the valve body 160 from the cutoff position 16e to the connection position 16f. This allows the hydraulic cylinder 12 to expand and contract and thus allow the rear wheel 11 to pivot. When the second excitation current PD2 is supplied to the solenoid 18, the solenoid 18 holds the valve body 160 in the connecting position 16f. As long as the second excitation current PD2 is supplied to the solenoid 18, the rear wheel shaft 11 is allowed to pivot. Since the value of the second excitation current PD2 is relatively small, the application of the current PD2 for a relatively long time does not overheat the solenoid 18.

While the high-side driver 32 outputs the first excitation current VP1, or during time T1, the microcomputer 31 checks the solenoid 18 using the diag signal VD. Since the duty ratio of the first excitation voltage VP1 is 100%, the duty ratio of the corresponding diag signal VP is also 100%. The high-side driver 32 outputs a diamond signal VD for a time T1. When the diag signal VD has a low voltage value, the coil of the solenoid 18 is shut off or shorted to the solenoid 18. In this case, the microcomputer 31 judges that there is a failure and the valve body 160 is moved to the blocking position 16e by the spring 17 so that the rear axle 11 is locked against pivoting. The application of voltage to the node 18 is stopped.

In addition, the high-side driver 32 is temperature sensitive. When the temperature of the high-side driver 32 reaches 150 ° C., the high-side driver 32 automatically reduces the value of the excitation voltage VP. This also locks the rear axle 11 against pivoting.

1 to 4 have the following advantages.

The controller 26 excites the solenoid 18 with the first exciting current PD1 and thus moves the valve body from the shutoff position 16e to the connecting position 16f. Then, the controller 26 transmits the second excitation current PD2 having a value smaller than the first excitation current PD1 to the solenoid 18 so as to maintain the valve body 160 at the connection position 16f. . Compared with the prior art, the valve body 160 is held in the connecting position 16f by a current having a relatively small value. The smaller value of the current for maintaining the position of the valve body 160 suppresses the excessive temperature increase of the solenoid 18.

The controller 26 supplies the first excitation current PD1 to the solenoid 18 for a time required to move the valve body 160 from the cutoff position 16e to the connection position 16f. Thus, the controller 26 does not need to detect the time when the valve body 160 is moved from the position 16e to the position 16f to determine when to switch the exciting current. This simplifies the structure of the controller 26.

The PWM circuit 39 generates the first and second excitation voltages VP1 and VP2 based on the first and second command signals SD1 and SD2 calculated by the CPU 31a. The high-side driver 32 applies the first and second excitation voltages VP1 and VP2 to the solenoid 18. This improves the supply of the first and second excitation currents PD1 and PD2 having different values.

The PWM circuit 39 outputs the first PWM signal PS1 having a duty ratio of 100% during the time T1. On the other hand, the microcomputer 31 determines whether the solenoid 18 is short-circuited or whether the solenoid 18 is electrically open. Therefore, the failure of solenoid 18 is detected by controller 26.

While the microcomputer 31 does not output the command signal PS, that is, while the rear wheel 11 is locked, the high-side driver 32 is a low-level diag signal from the diag terminal DIAG. (VD) Continue output. At this time, the value of the diamond signal VD allows the microcomputer 31 to determine whether the solenoid 18 has a failure.

The CPU 31 maintains the internal resistance of the solenoid 18 at the maximum possible temperature of the voltage detector 30, the minimum current Ih and the solenoid 18 to maintain the valve body 160 in the connection position 16f. The second excitation current PD2 is calculated based on the power supply voltage VB detected by. Therefore, the value of the second exciting current PD2 is controlled by changing the power supply voltage VB. This structure also saves power of the battery 27 by suppressing heat of the solenoid 18.

Intelligent high-side driver 32 is applied in place of conventional current detection circuits including transistors, operational amplifiers and resistors. Thus, the controller 26 reduces the number of parts. In addition, the high-side driver 32 is directly connected to the CPU 31a without the need for intervening an analog-to-digital converter. This simplifies the structure of the controller 26.

Now, a control device of the solenoid valve according to the second embodiment of the present invention will be described. The apparatus of the second embodiment is different from the first embodiment of applying another excitation voltage to the solenoid.

As shown in FIG. 5, the excitation current PD may include two currents PD1 and PD2 and has a predetermined cycle. The first exciting current PD1 is applied to the solenoid 18 for a predetermined time TI (eg, 1 second). Thereafter, the second current PD2 is supplied to the solenoid 18 for a predetermined time T2 (for example, 3 seconds). The first excitation current PDI is supplied to the solenoid 18 for at least a portion of the predetermined time interval T, which is the sum of the times T1 and T2. Therefore, the valve body 160 is firmly held at the connecting position 16f.

In the second embodiment, the duty ratio of the second excitation voltage VP2 is Dh% and the duty ratio of the diamond signal VD is Dh%. That is, each pulse of the diag signal VD is output from the high-side driver 32 for a relatively short time. Therefore, while the high-side driver 32 applies the second excitation voltage VP2 to the solenoid 18, or during time T2, the microcomputer 31 has failed based on the diamond signal VD. Cannot be judged.

In the embodiment of FIG. 5, the first PWM signal PS1 having a duty ratio of 100% is intermittently output. This allows the CPU 31a to determine whether the solenoid 18 has a failure every time the first excitation current PD1 is output.

A third embodiment of the present invention will be described with reference to FIG.

In the third embodiment, the high-side driver 32 is replaced with a current detection circuit 42 comprising a comparator and a controller, a transistor 41 and a current limiting circuit 44 for limiting excess current. The current detection circuit 42 detects the value of the current supplied to the solenoid 18. The detection signal generated by the circuit 42 is input to the microcomputer 31 through the analog-to-digital converter 43. When the PWM signal PS is not output, if the circuit 42 detects a current larger than a predetermined value, the microcomputer 31 determines that there is a short circuit between the solenoid 18 and the battery 27. . On the other hand, when the PWM signal PS is output, if the circuit 42 detects a current larger than a predetermined value, the microcomputer 31 electrically opens the circuit (for example, the solenoid 18 is cut off). I think it is.

Current limiting circuit 44 includes a pair of transistors and resistors. When there is a short circuit in solenoid 18, circuit 44 prevents solenoid 18 from receiving excessive current.

The invention will be applicable to those skilled in the art in many other specific forms without departing from the spirit or scope of the invention. In particular, it will be appreciated that the present invention can be applied in the following forms.

In the above-described embodiment, the controller 26 is used for the forklift to control the pivoting of the rear wheel shaft 11 based on the load W and the fork height H. However, the present invention can be applied to a forklift which controls the pivoting of the rear axle based only on the fork height or the load of the load, the fork height and the inclination of the mast. In other cases, the controller 26 prevents the solenoid 18 from exciting the coil 18 and overheating by the flow of hydraulic oil and the heat of the engine.

The value of the second excitation current PD2 may be constant as long as it is larger than the minimum current Ih. In this case, the controller 26 reduces the heat generated while the valve body 160 is held at the connecting position 16f.

The solenoid valve 16 may have a position sensor to detect the movement of the valve body 160 to the connection position 16f. When detecting that the valve body 160 moves to the connection position 16f based on the signal of the position sensor, the controller 26 stops supplying the first excitation current PD1 to the solenoid 18, The second excitation current PD2 starts to be supplied to the solenoid 18.

The duty ratio D of the first excitation current PD1 is not necessarily 100% and may be smaller than 100%. If the duty ratio D is less than 100%, it is difficult to detect shorts and interruptions in the solenoid 18. However, heat generation of solenoid 18 can still be suppressed.

The valve controller 26 according to the invention may be applied to a mechanism other than an axial locking mechanism. For example, the controller 26 may be used in a mechanism for controlling the inclination of the fork and the mast. The tilt control mechanism includes a hydraulic circuit having a hydraulic pump, a tilt cylinder, a manual flow control valve and an electromagnetic flow control valve. The oil pump supplies hydraulic oil to the inclined cylinder via manual and solenoid valves. The driver controls the opening amount of the manual valve by operating the inclined lever. The solenoid valve controls the flow of oil from the manual valve to the inclined cylinder. In particular, the solenoid valve switches the flow rate between two fixed values.

The solenoid valve of the inclination control mechanism includes a valve body and a solenoid. When the valve body is disposed in the shut off position by the ug means, the solenoid valve increases the flow rate from the manual valve to the inclined cylinder. When the solenoid is excited, the valve body is moved to the connecting position. In this state, the solenoid valve reduces the flow rate of oil from the manual valve to the inclined cylinder.

The inclination control mechanism keeps the valve body in the closed position if the load on the fork is relatively light and the fork is in a relatively low position, thus allowing the mast to incline quickly according to the operation of the incline lever. When the load on the fork is relatively heavy and the fork is in a relatively high position, the inclination control mechanism moves the valve element to the connecting position, thereby causing the mast to incline slowly according to the operation of the inclination lever. The inclination control mechanism may include a solenoid valve controller 26 according to the present invention.

The valve controller 26 according to the invention is suitable for suppressing the heat generation of the solenoid. Thus, the valve controller 26 may be used in an industrial vehicle in addition to the forklift.

Therefore, the present examples and embodiments are not limited by the detailed description herein and may be modified within the scope of the appended claims.

The Bangbang and apparatus according to the present invention relate to a mechanism for controlling the pivoting of a rear axle in an industrial vehicle such as a forklift, and more particularly to a method and apparatus for controlling an solenoid valve in a hydraulic circuit of a pivot control mechanism.

Claims (16)

The control method of the solenoid valve 16 which includes a power supply, the solenoid 18 excited by a power supply, and the valve body 160 switched between a 1st position and a 2nd position, and shifted toward a 2nd position. In A) a supplying step of supplying a moving current PD1 to the solenoid 18 for moving the valve body 160 from the second position to the first position, B) a supply step of supplying the solenoid 18 with a holding current PD2 having a value smaller than the moving current PD1 after the step a) to maintain the valve body 160 in the first position. Control method of solenoid valve The method of claim 1, wherein the step of calculating the value of the holding current PD2 is Detecting a current voltage VB of the power supply; Storing the reference current Ih in advance to maintain the valve body 160 at the first position and the reference resistance Rsol of the solenoid 18 at a predetermined temperature of the solenoid 18; Calculating a coefficient Dh using the following equation based on the current voltage VB, the reference current Ih and the reference resistance Rsol of the power supply, [Equation 1] Dh> reference current (Ih) / (current voltage (VB) / reference resistance (Rsol), Dh <100% Multiplying the calculated moving current PD1 by the calculated coefficient Dh to obtain the holding current PD2 having the value of the holding current PD2 slightly larger than the value of the reference current Ih and smaller than the value of the moving current PD1. The control method of the solenoid valve comprising a. 3. The method of claim 2, wherein the moving current PD1 and the holding current PD2 are pulse waves each having a different duty ratio, and the coefficient Dh is a duty ratio of the holding current PD2. The control method of the solenoid valve characterized in that. Controller 26 for controlling a solenoid 18 that is energized by a power source and a solenoid valve 16 that includes a valve body 160 that is switched between first and second positions and is biased toward a second position. To The controller 26 A driver 32 for applying a voltage to the solenoid 18, A processor 31 for sending a command to the driver 32 indicating a value of the voltage to be applied to the solenoid 18, When moving the valve body 160 from the second position to the first position, the processor 31 applies the movement command signal PS1 to apply the moving voltage VP1 to the solenoid 18 for a predetermined time T1. Transfers to 32, and when holding the valve body 160 in the first position, the processor 31 calculates a holding current PD2 slightly greater than the minimum current for holding the valve body 160 in the first position. In order to apply the holding voltage VP2 to the next time T1, the holding command signal PS2 is transmitted to the driver 32, and the holding voltage VP2 transmits the holding current PD2 to the solenoid 18. A controller for controlling the solenoid valve, characterized in that for generating. 5. The voltage sensor according to claim 4, further comprising: A memory for storing the reference current Ih and the reference resistance Rsol of the solenoid 18 at a predetermined temperature of the solenoid 18 to maintain the valve body 160 in a first position, The processor 31 calculates the coefficient Dh based on the current voltage VB, the reference current Ih, and the reference resistance Rsol of the power supply, and the coefficient Dh calculates the value of the holding current PD2. A controller for controlling a control valve, characterized in that it is used to set. 6. A controller as claimed in claim 5, wherein the predetermined time (T1) is slightly longer than or equal to the time required for the valve body (160) to move from the second position to the first position. 7. The controller as claimed in claim 6, wherein the moving command signal (PS1) and the holding command signal (PS2) are pulse signals each having a different duty ratio. 8. The driver 32 according to claim 7, wherein the driver 32 performs a pulse width displacement of the voltage from the power supply according to the duty ratio of the movement command signal PS1, and the shifted moving voltage VP1 is transferred to the solenoid 18. A controller for controlling the control valve, characterized in that applied to the solenoid (18) to generate a current corresponding to (VP1). 8. The driver 32 according to claim 7, wherein the driver 32 performs pulse width modulation of the voltage from the power supply according to the duty ratio of the sustain command signal PS2, and the modulated sustain voltage VP2 is applied to the solenoid 18. A controller for controlling the control valve, characterized in that applied to the solenoid (18) to generate a current corresponding to (VP2). 10. The controller as claimed in claim 9, wherein the duty ratio of the movement command signal (PS1), the movement voltage (VP1), and the movement current (PD1) is 100%. 10. The controller according to claim 9, wherein the duty ratio of the sustain command signal (PS2), the sustain voltage (VP2), and the sustain current (PD2) is less than 100%. 8. The solenoid 18 includes a current sensor 32; 42 for detecting a current, wherein the processor 31 has a solenoid current and a hold command signal detected by the current sensor 32; A controller for controlling the control valve, characterized in that for checking the failure of the solenoid (18) based on the level of (PS2). 13. A controller as claimed in claim 12, characterized in that the failure of the solenoid (18) is a short circuit between the power supply and the solenoid (18) or the disconnection of the solenoid (18). 13. The controller according to claim 12, wherein the processor (31) outputs a movement command signal (PS1) periodically when the valve body (160) is held in the first position. 15. The controller according to claim 14, wherein the current sensor (32; 42) is integral with the driver (32). 8. The control valve (16) according to claim 7, wherein the control valve (16) is used in the hydraulic circuit of the axis pivot control mechanism for an industrial vehicle, wherein the controller (26) controls the opening amount of the control valve (16). Controller for controlling.